Technique requires radio frequency induction power source, induction furnace and good vacuum system to induce brittle material thermal shock testing

King, C. R.

Rowley, J. C.

English

NASA Technical Reports Server

May, 102	 B72-10228 
•	 NASA TECH BRIEF 
Space Nuclear Systems Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Simple, Reproducible Methods for Thermal

Shock Testing of Brittle Materials 
Induction	 Induction 
Power Supply	 Furnace 
Diffusion 
Pump 
APPARATUS 
The problem: 
The screening of prospective brittle materials for the 
Nuclear Rocket dictated the need for a thermal shock 
test which was quick, uncomplicated, and did not re-
quire a complete evaluation of the material's mechanical 
or thermal properties. Various single-cycle thermal-shock 
tests existed, but were generally difficult to control. 
They could not be used satisfactorily for carbide com-
posites and grahites which represent about fifty per-
cent of all brittle materials.
View Port 
Pyrex 
Mantle 
Test 
Specimen 
Current 
Concentrator 
Induction 
Coil
Vacuum 
System 
INDUCTION FURNACE 
How it's done: 
Only three pieces of equipment are required: a radio-
frequency (rf) induction power source, an induction 
furnace, and a reasonably good vacuum system to pre-
vent specimen oxidation during heating. The most im-
portant of the three is the power source (400 kHz at 
50 kW), with "hard-start" characteristics since "soft-
start" generators do not reach full power rapidly. Be-
cause the highest current density occurs at the outer 
diameter of the test specimen immediately adjacent to 
the concentrator, most of the heating occurs within a 
very thin peripheral layer of the specimen. Power re-
The solution: 
A technique has been developed which induces ther-
mal shock testing of brittle materials using radio. 
•	 frequency power, without mechanical restraint of the 
specimen.
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000228 2020-03-17T03:33:13+00:00Z
mains on until fracture occurs or until a steady-state 
radial temperature is established. The steady-state con-
dition takes place in about 2 seconds; fractures occur in 
about 1/2 second. The instant of fracture is determined 
by an acoustic wave emission device attached to the 
furnace. Seven samples have been run on each of 20 
different materials in 6 hours with excellent reproduci-
bility. In contrast, previous testing involving thermal 
conductivity would have required one week over a 
range of temperatures for a single sample of one 
material. 
The technique is useful for virtually all materials, 
except those which are good electrical insulators, such 
as glass, since adequate rf coupling cannot be induced 
into them. An above average high school student could 
be trained to run repeatable tests in about two hours.
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
AEC-NASA Space Nuclear Systems Office 
U.S. Atomic Energy Commission 
Washington, D.C. 20545 
Reference: B72-10228 
Patent Status: 
No patent action is contemplated by the AEC or 
NASA.
Source: J.C. Rowley and C.R. King of 
Los Alamos Scientific Laboratory
under contract to
Space Nuclear Systems Office 
(NUC-1 1020) 
B72-10228	 Category 06


Simple, reproducible methods for thermal shock testing of brittle materials

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server